\documentclass{article}     \usepackage{multicol}
 \textheight15cm \textwidth7cm \parindent0mm \parskip 1ex plus2ex minus0.8ex
\begin{document}
\section*{9. Delimiters:}

\begin{multicols}{2}
$\left(            \right. $ \verb|:\left(|\\ 
$\left)            \right. $ \verb|:\left)|\\ 
$\left[            \right. $ \verb|:\left[|\\ 
$\left]            \right. $ \verb|:\left]|\\ 
$\left\{           \right. $ \verb|:\left\{|\\ 
$\left\}           \right. $ \verb|:\left\}|\\ 
$\left|            \right. $ \verb+:\left|+\\ 
$\left\|           \right. $ \verb+:\left\|+\\ 
$\left/            \right. $ \verb|:\left/|\\ 
$\left\backslash   \right. $ \verb|:\left\backslash|\\ 
$\left\lfloor      \right. $ \verb|:\left\lfloor|\\ 
$\left\lceil       \right. $ \verb|:\left\lceil|\\ 
$\left\langle      \right. $ \verb|:\left\langle|\\ 
$\left\uparrow     \right. $ \verb|:\left\uparrow|\\ 
$\left\downarrow   \right. $ \verb|:\left\downarrow|\\ 
$\left\updownarrow \right. $ \verb|:\left\updownarrow|\\ 
$\left\rfloor      \right. $ \verb|:\left\rfloor|\\ 
$\left\rceil       \right. $ \verb|:\left\rceil|\\ 
$\left\rangle      \right. $ \verb|:\left\rangle|\\ 
$\left\Uparrow     \right. $ \verb|:\left\Uparrow|\\ 
$\left\Downarrow   \right. $ \verb|:\left\Downarrow|\\ 
$\left\Updownarrow \right. $ \verb|:\left\Updownarrow|\\ 
$\left.    \,\,\,  \right. $ \verb|:\left.|
\end{multicols}

$\left( \int\limits_{a}^{b} (x+1)(x-1)\,dx \right)^{2}$      \\[+2ex]
$\left(x_1,\ldots,x_n\right) $                               \\[+2ex]
\end{document}
